Voltage step-down signal device



Jan. 10, 1961 I H. SMITH 2,967,955

VOLTAGE STEP-DOWN SIGNAL DEVICE Filed May 13, 1957 FIG. /Z

INVENTOR HENRY SMITH AGENT VOLTAGE STEP-DOWN SIGNAL DEVICE Henry Smith,Central Valley, N.Y., assignor to J. & H. Smith Manufacturing Company,Newlmrgh, N.Y., a partnership of New York Filed May 13, 1957, Ser. No.658,731

7 Claims. (Cl. 307-157) This invention relates to signal devices andmore particularly to combined voltage step-down and indicator lightassemblies.

The requirements for indicator light assemblies vary a great dealdepending upon the uses to which they are put. The more or lessconventional pilot light assemblies, found on test display boards andused in connection with general electronic equipment, are ordinarily ofa simple, cheap and flimsy construction. More critical are thoseindicator lights engineered to perform satisfactorily under the adverseconditions found in military applications as well as certain ruggednon-military installations. In these latter areas, a prime requisite foran indicator light is one which is sturdy and shockproof, compact, andmoisture resistant, as well as one reasonably inexpensive tomanufacture. Hence, the principal object of the present invention is toprovide a signal device to satisfy these needs.

A further object of the invention is to provide an indicator lightincorporating means for stepping down operating voltages, and arrangedso as to contribute to the manufacturing superiority of the over-allsignal device.

Heretofore, the usual means employed to obtain lower working voltagesfrom a more or less standard source have included, inter alia,transformers. These allow satisfactory voltage reductions Wheneverrugged service requirements are absent. Economically they may bejustified when lower or different operating voltages must be providedfor a number of functions, including indicator lights. Even here,however, the problems of wire breakages and their resultant shortcircuits, weight and size disadvantages, excessive heat losses, etc.tend to mitigate the possible broad advantage obtained by employing suchvoltage step-down means.

Yet another method of obtaining voltage step-down has been employed; itis the use of capacitors, which means is a substantially cheaperexpedient, particularly where the number of signaling devices to befurnished the lower operating voltage is limited. But here too, problemsarise. The prevention of surge current, which may burn out signalelements or otherwise interfere with the proper operation of indicatorlight assemblies, is a problem to which transformers are not subject.For example, if alternating-current power is supplied to an indicatorlight assembly which is in series with a conventionally fabricatedcapacitor, the random possibility exists that the connection will bemade when the supply voltage is near a maximum excursion. If thishappens, the resultant high current surge may burn the lamp filamentout. Destruction may be avoided if the lamp is underrated or if it has ahigh resistance, but both of these preventatives have their owndisadvantages. is accompanied by a small light output, unless the sizeof the capacitor is increased, while the latter necessitates a longerand more fragile filament which, in turn, is more susceptible to shock.Some designers, rather than The former atent O 2,967,955 Patented Jan.10, 1961 settle for less illumination or specify larger capacitors,employ separate resistors and/or non-linear devices, e.g., varistors, toprevent the deleterious effects of surge current. These alternatives arenot without their own special drawbacks, principal among which are cost,weight and size.

Therefore, another object of the present invention is to provide asignaling device having integral voltage stepdown means which are notaffected by surge currents.

A feature of the invention, in accordance with this latter object,pertains to the use of metallized film capacitors of the self-healingtype. In these capacitors, a thin layer of aluminum or some otherconductive metal is deposited on the dielectric material (e.g. Mylar) toact as an electrode. Two sheets of these electrodes are wound to formthe capacitor. This type of capacitor has a number of advantages. Mostimportantly, temporary short circuits, which occur due to a break orweak spot in the dielectric, are burned out. This results from thealuminum deposit adjacent the weak spot oxidizing to reestablish thedielectric insulating bond between the capacitor plates. Provided thethickness of the metallic deposit is kept sufficiently small, shortcircuits will burn out and the capacitor will continue to operate as itshould without creating a permanent short circuit. These metallized filmcapacitors also take up less space than their more conventionalcounterparts.

The particular structure employed in the instant invention is designedto facilitate the manufacture of an inexpensive and reliable capacitivevoltage step-down indicator assembly, and hence, it has a number ofnovel features designed to further such purpose. One particular featureof the invention is a split body construction to reduce the deleteriouseffects of vibrations throughout the light assembly as Well as tofacilitate inexpensive assembly. The cylindrical body is formed of twohalfcylinders of a suitable molded resin. The parts are mirrors, i.e.,each is formed in the same die, and contain cavities along theirdiametral sides, which cavities cooperatively maintain the electricalconnectors that link the capacitor electrodes and lamp terminals, intheir correct positions. This construction obviates the need for anyscrews, welding or diverse means to maintain the electrical connectorsproperly positioned in the interior of the indicator light assembly.

Another feature of the invention pertains to the use of a cylindricalsleeve threaded on its outer surface and which fits over the upperportion of the body to maintain the body assembly together when the twoparts thereof are in contiguous positions along their plane surfaces.Threadedly engaging the outer threaded surface of the sleeve is aconventional lens or jewel holder.

Another feature pertains to the use of an intermediate external portionof the body assembly as a mandrel for the metallized film capacitor,with provision being made to connect the proper electric connectors tothe capacitor electrodes. Thin conductive tapes attached to theelectrical connectors are threaded through cooperating aperture of thebody and are appropriately interleaved in the capacitor winding tocontact the plates of the capacitor. This makes it unnecessary toprovide any means for soldering or otherwise terminating the capacitorplates at the terminals.

Yet another feature of the capacitor relates to the manner in which itis connected. The two connecting tapes are interleaved in the winding sothat each capacitor plate is contacted at an opposite end of the windingand at one point only. As a consequence, the current in each capacitorplate must flow in a convolutional path of considerable length ascompared to the flow of current in the conventional capacitor. In thelatter, connections are often multipled to the edges of each capacitorplate which requires the charging current to flow only a short distancebetween the electrodes. As .a result, virtually no resistance componentis present in most capacitors. Contrariwise, the end-to-end type ofconnection is used to introduce a considerable resistance, and someinductance into the capacitor circuit. This built-in resistive-inductiveefiect acts as an effective surge suppressor during transient periodswithout unduly affecting the steady-state condition.

A further feature of the invention relates to the use of anencapsulating resin, such as an epoxy resin, to retain the body andthreaded sleeve in fixed relation and to enclose the capacitor toprotect it and related parts of the indicator light assembly. With theencapsulating resin substantially surrounding the body and metallizedtape capacitor, a compact, sturdy and moisture resistant voltagestep-down indicator light assembly is assured.

These and other objects and features of the invention may be more fullyunderstood when the following description is read with reference to thedrawings in which:

Fig. l is a perspective of a complete indicator light assembly as itmight be aifixed to a panel mounting;

Fig. 2 is an exploded perspective of the half-cylindrical piece-partswhich form the body assembly as well as the electrical connectors whichare positioned within the body;

Fig. 3 is a partial cross-section along a diameter of the complete pilotlight assembly of Fig. 1;

Fig. 4 is a perspective of part of the body assembly with the metallizedfilm capacitor partially wound thereon; and

Fig. 5 is the metallized film capacitor unwound to show its constructionand orientation With respect to terminal connectors.

Looking more in detail at Fig. 1, it will be seen that the indicatorlight assembly includes a resin encapsulated body it) which may fitflush against a mounting panel 12. where it is firmly held by a nut 13threadedly engaging cooperating sleeve 11. Sleeve 11 is held along itslower shoulder 54 (Fig. 3) by the epoxy resin en closing the capacitor59 and light body 20. The lamp filament or bulb 44 extends above upperparts 21 (a, b) of the body 2d (a, b). A threaded cap 14 with a jewel orlens 15 mounted therein is provided to threadedly engage sleeve 11.

Turning to Figs. 2 and 3, which more particularly disclose therelationship between the various parts, it can be seen that the bodycomprises two identical or mirror parts 245a and 20b. In the exemplaryembodiment of the present invention, the body parts 20a, b are molded byemploying one of the polyamide resins, e.g. such as commercial nylon. Atypical one of these parts, for example, 2%, can be seen to be of asemicylindrical shape with different radii cross sections along itsvertical or longitudinal axis. The shoulders 22 (a, b) and 24 (a, b) actas guides or retainers for the metallized tapes 611, 62 (Fig. 4) thatform the capacitor 59. The capacitor 59, of course, is wound onintermediate portion 23 (a, b) of the body 2%, which portion acts as amandrel. The uppermost portion 21 (a, b) of the body 20 is the retainingmeans for the inner portion or aperture of the sleeve 11 (Fig. 3). Whenthe parts of the body 20a and 20b are placed together, the sleeve 11slides over the outer diameter thereof and abuts the upper surface ofthe shoulder 22 (a, b).

The flat surface of each semi-cylindrical half of the body 20 has formedin it a number of cavities 25, 27, 28, 29, 3%, 31, and 32, allpre-arranged to properly support the electrical connectors 41, 44, and47 in their respective positions.

The piece-parts which form the electrical path for signal lamp 441* andthe capacitor 59 include an L-shaped terminal 41 having a threadedaperture through its lower end 43which cooperates with a screvv'StB. Onthe upper end of the terminal 4-1 is fixedly retained a signal lightreceptacle 42 of cylindrical, open-ended, construction. The surfacesdefining the aperture through the receptacle 42 are threaded tocooperate with a signal element 40 having a threaded base. A second,S-shaped, terminal 44 is provided, which terminal has an upper fiatportion 45 and a lower end 46 threadedly apertured to cooperate with ascrew 5h. A thin stainless steel tape 52, which acts as one of the leadsto connect the capacitor in series with the filament of lamp 40, isconnected to the vertical portion of the S-terrninal 44. The strip 52,which is two to three mils thick, is linked through rectangular aperture55 in terminal 44 and thereafter spotwelded or otherwise afiixed to theintermediate portion of terminal 44. And, finally, a connector 47 isprovided, it also being S-shaped, which has an upper part 48 and a lowerpart 49. Welded to the lower end 49 of the connector 47 is a second thinstainless steel tab 53 which acts as the other terminal for capacitor59.

Considering these electrical connectors and terminals in relation to thecavities illustrated in shell 20b of the body assembly 20, and dupicated in shell 20a, their 'ultimate positions may be noted. Theterminal 41 fits in the left vertical groove 2% with its lower end 43residing in the cavity 31b and the receptacle 42 fitting into the cavity25b. The second terminal 44 fits in the right vertical groove 3% withits lower end 46 disposed in cavity 32b, while its upper portion 45 fitsinto horizontal groove 28b. The intermediate connector 47 lies betweenterminals 41 and 44 inthe upper portion of vertical groove 30b with itsupper part 48 resting on surface 26b and its lower end 49 fitting intohorizontal cavity 27b. The tab 53 extends downwardly from cavity 27bover the notched portion 33b of the body Ztl, which notch prevents thetab 53 from extending beyond the outer surface of shoulder 22. Thisassures a close fit between sleeve 11 and shoulder 22 withoutendangering strip 53 or capacitor 59. A washer 51 abuts terminal 41below the receptacle 42 to insulate it from the upper part 43 of theintermediate connector 47. With these parts so positioned, the bodypiece-parts 20a and 20b are ready to be put together along their fiatsurfaces. It will be observed (Fig. 3) that the strip 52, attached tothe terminal 44, extends outside the split body assembly 20 from betweenthe cooperating flat surfaces and thereafter curves around the mandrelportion 23 of the body 20.

With the electrical connectors 41, 44, and 47 held fixed in their propercavities by fitting the two parts of the body 20 together, the mandrel23 is ready to have the metallized film capacitor 59 wound thereon.

Looking to Figs. 4 and 5, which illustrate more clearly the constructionof the capacitor 59 itself, it can be seen that the capacitor 59comprises a pair of dielectric film strips 61 and 62 which havedeposited on one of their sides a thin coating of aluminum 63 and 64which is approximately 40 to 50 millimicrons in thickness. Any suitablecondenser paper may be used, but one of the most popular is Mylar whichis a tough and durable dielectric. Approximately 10 percent of thealuminum coating on each film is oxidized so that when the metallizedpapers or films are placed one on top of the other, as illustrated inFig. 5, an overlap of approximately eighty percent is obtained. Atypical plate type capacitor is formed when terminals, e.g., such asstrips 52 and 53, are connected to respective metallized surfaces 63 and64. Fig. 5 depicts the construction of the capacitor 59 before it iswound on the mandrel 23. The steel strips 52 and 53 which are ultimatelyconnected to opposite ends of the two capacitive plates, are shown inphantom in these figures to clarify the way in which the connections aremade, an important aspect of the invention since it is the key to thebuilt-in resistance of the capacitor. It will be noted (Fig. 5) that theinner metallized strip 61 extends further to the left of the drawingthan does strip 62 which underlies it. In the 'same manner,metallized'strip 62 extends further to the right of the drawing thandoes strip 61. This is to assure that when the film capacitor 59 iswound around the mandrel 23, the terminal strip 52 will engage themetallic surface 63 of tape 61 at one end thereof and that the strip 53will engage the opposite end of strip 62 on metallic surface 64. Therelationship of the capacitor 59 to the mandrel 23 and the lowershoulder 24 of the body 20 is shown in Fig. 4 with the terminalconnections 52 and 53 in phantom. Actually, the width of the metallizedtapes 61, 62 are less than the width of the mandrel (see Fig. 3) so thatno ditficulty is experienced in winding the capacitor 59 thereon.

Fig. 3 depicts the assembled pilot light assembly in cross-section withthe terminals and connector properly positioned and with the metallizedfilm capacitor 59 connected end-to-end to the terminal strips 52 and 53.Fig. 3 additionally illustrates the way in which the encapsulating resincover engages the lower shoulder 54 on the sleeve 11 to hold it firmlyin position on the body 20. The mold (not shown) for forming this cover10 also permits the resin to hook over a portion of the lower surface ofshoulder 24 on the body 20.

In the particular embodiment herein disclosed, a capacitor ofapproximate 0.9 mfd. is obtained by employing 275 turns, more or less.The eflective resistance of capacitor 59, end connected, is in the orderof 600 ohms. The energization of the indicator light assembly from aconventional 115 volt, 60 c.p.s. alternating current source when thelight filament is a low drain one, such as 0.04 amps at 6 volts, assuresa pilot light assembly which is substantially impervious to surgephenomena. Voltage variations of plus or minus 10 volts and frequencyvariation of plus or minus five percent are immaterial. It is apparent,of course, that the efiective resistance and capacitance may be variedto cooperate with different power sources.

It will be observed that the component parts and assembly techniquesemployed in fabricating the present invention have a number ofadvantages. The use of mirror parts for the body assembly cooperatingwith conductively connecting parts which maintain their correctpositions without further operations simplifies manufacture andassembly. Terminating the capacitor without resorting to soldering orother more complex afiixing operations compounds the assemblyadvantages. The over-all effect is a compact, inexpensive and sturdycombination stepdown voltage and indicator light device. The devicerequires no critical parts or tolerances, and further, it requires noskilled operators to assemble it.

It is to be understood, of course, that the abovedescribed arrangementsare merely illustrative of the application of the principles of theinvention. Numerous other arrangements may be devised by those skilledin the art without departing from the spirit and scope of the invention.

What is claimed is:

l. A combined voltage step-down and signal device comprising a signalelement, a two-piece molded body having two shoulders which form amandrel, said body piece-parts formed with interior cavities, a firstterminal having a receptacle for said signal element afiixed at one end,conductive strips attached to a second terminal and a connector, saidterminals and connector supported properly in said cavities whereby saidconductive strips extend outside of said body formed of saidpiece-parts, a film capacitor having a pair of electrodes and wound onsaid mandrel so that one electrode at one end of said capacitor contactsthe strip afiixed to said second terminal and the other electrode at theother end of said capacitor contacts the strip afiixed to saidconnector, said capacitor, terminals and connector completing a serieselectrical path for said signal element, a sleeve fitting over a part ofsaid body, means for connecting a source of alternatingcurrent power tosaid terminals, and unitary means enclosing said capacitor and said bodyand retaining said sleeve on said body.

2. A voltage step-down and indicator light assembly comprising, incombination, a signal element, a two-piece molded body of circular crosssection having two shoulders which form a mandrel, said body piece-partsformed with cooperating internal cavities, a first terminal having areceptacle for said signal element aflixed to its upper end, conductivestrips attached to a second terminal and a connector, said terminals andconnector supported in proper relation to each other in said cavitieswhereby said conductive strips extend outside of said body formed ofsaid piece-parts, a film type capacitor including two contiguous sheetsof translucent dielectric upon which have been deposited thin metallicdeposits to act as first and second electrodes, said first electrodehaving a portion extending beyond said second electrode at one end ofsaid film capacitor and said second electrode having a portion extendingbeyond said first electrode at the other end of said film capacitor,said capacitor wound on said mandrel whereby the extending portion ofsaid first electrode contacts the strip affixed to said second terminaland the extending portion of said second electrode contacts the stripafiixed to said connector, said capacitor, terminals and connectorcompletinga series electrical path for said signal element, a tubularmember having a shoulder at its lower end and at its outer surfaceretaining a cap and lens assembly which cooperate with said signalelement, said tubular member cooperating with said body whereby theshoulder of said tubular member telescopes over a part of said body andabuts one of the shoulders of said body, means for connecting a sourceof alternating-current power to said terminals, and a unitary cover ofthermosetting resin enclosing said capacitor and said body and retainingsaid sleeve shoulder adjacent said body shoulder.

3. A combined voltage step-down and signal device for visual displaypurposes comprising, in combination, a two-piece body of circular crosssection having two shoulders which form a mandrel therebetween, saidbody piece-parts formed with predesigned internal cavities, a signalelement mountable within said body, a plurality of terminals forconnecting said signal element to a source of alternating-current power,said terminals disposed in the cavities of said body, a film capacitorhaving first and second electrodes, said capacitor wound on said mandrelso that said first and second electrodes are serially connected in saidsignal element circuit at the opposite ends of said capacitor, a sleevesupporting a lens assembly for said signal element and fitting over apart of said body to hold said body piece-parts together, and aninsulating means enclosing said capacitor and said body and a portion ofsaid sleeve.

4. A signal device comprising, in combination, a split body having amandrel thereon, a signal element mountable within said body, aplurality of terminals for connecting said signal element to a source ofalternatingcurrent power, means integral with said body for supportingsaid terminals Within said body, a convolution-a1 film capacitor havingfirst and second electrodes and wound on said mandrel so that saidelectrodes are serially connected in said signal element circuit atopposite ends of the capacitor, a sleeve fitting over a part of saidbody to hold said split body together, and an insulated cover enclosingsaid capacitor, said body and a portion of said sleeve.

5. A signal device comprising, in combination, a split body having amandrel integrally formed thereon, terminals and at least one signalelement supportable within said body and cooperating with saidterminals, a capacitor wound on said mandrel, and means including saidterminals for serially connecting end-to-end the electrodes of saidcapacitor with said signal element.

6. A voltage step-down and signal device comprising, in combination, atwo-piece body of circular cross section having two shoulders which forma mandrel therebetween, said body piece-parts formed with internalcavities, a signal element, a plurality of terminals for connecting saidsignal element to a source of alternatingcurrent power, said terminalssupported in some of the cavities of said body, a film type capacitorincluding contiguous sheets of dielectric upon which have been depositedmetallic particles to act as first and second electrodes, said firstelectrode having a portion extending beyond said second electrode at oneend of said film capacitor and said second electrode having a portionextending beyond said first electrode at the other end of said filmcapacitor, said capacitor wound on said mandrel whereby said first andsecond electrodes are serially connected in said signal element circuitby their respective extended portions, a sleeve supporting a lensassembly and having a shoulder at one end, said sleeve fitting over aportion of said body whereby the shoulder of said sleeve abuts one ofthe shoulders of said body and said lens assembly cooperates with saidsignal element, and a unitary insulated body enclosing said capacitorand said body and retaining said sleeve shoulder adjacent said bodyshoulder.

7. A voltage step-down and indicator light assembly for visual displaypurposes comprising, in combination, a signal element having twoterminals, a two-piece body of circular cross section, formed ofsimilar, half-cylinder piece-parts and having upper and lower reducedradii sections, said piece-parts having predesigned cavities formed intheir cooperating diametral sides, an L-shaped terminal having anopen-ended cylindrical receptacle affixed to its upper end and a powerconnector at its lower end, an S-shaped terminal having a powerconnector at its lower end and a thin strip of conductive materialattached to its intermediate portion, an S-shaped connector having athin strip of conductive material attached to its lower end, aninsulated washer to electrically separate said L-shaped terminal andsaid connector, said terminals, connector and washer supported in properrelation to each other in some of said cavities whereby said conductivestrips extend outside of said body formed 'of said piece-parts and yetnot beyond the outermost periphery of said body, a film type capacitorincluding two contiguous sheets of translucent dielectric upon whichhave been deposited thin deposits of metal to act as first and secondelectrodes, said first electrode having a portion extending beyond saidsecond electrode at one end of said film capacitor and said secondelectrode having a portion extending beyond said first electrode at theother end of said film capacitor, said capacitor wound on said lowerreduced radius portion of said body whereby the extending portion ofsaid first electrode contacts said conductive strip afiixed to saidS-shaped terminal and the extending portion of said second electrodecontacts said conductive strip affixed to said connector, saidcapacitor, terminals and connector in situ completing an electrical pathfor said signal element when one of said terminals of said signalelement engages said receptacle and the other of said terminal contactsthe upper part of said connector, a cyiindrical sleeve having a shoulderat its lower end and threaded on its outer surface to retain a cap andlens assembly, said sleeve fitting over the uppermost reduced radiussection of said body such that the shoulder of said sleeve abuts thebody shoulder formed between the two reduced radii parts of said body,means cooperating with said connectors of said terminals to connect asource of alternating-current power thereto, and a unitary insulatedbody of thermosetting resin to enclose said capacitor and said body andto retain said sleeve shoulder adjacent said body shoulder.

Thompson Oct. 14, 1941 Smith et al. Apr. 23, 1957

